Prerequisites for EoMPLS

Before you configure EoMPLS, ensure that the network is configured as follows:

•Configure IP routing in the core so that the PE routers can reach each other through IP.

•Configure MPLS in the core so that a label switched path (LSP) exists between the PE routers.

Restrictions for EoMPLS

•EoMPLS in Cisco IOS Release 15.1SY does not support load balancing at the tunnel ingress; only one Interior Gateway Protocol (IGP) path is selected even if multiple IGP paths are available, but load balancing is available at the MPLS core.

•Ensure that the maximum transmission unit (MTU) of all intermediate links between endpoints is sufficient to carry the largest Layer 2 packet received.

•If QoS is disabled globally, both the 802.1p and IP precedence bits are preserved.

•When the QoS is enabled on a Layer 2 port, either 802.1q P bits or IP precedence bits can be preserved with the trusted configuration. However, by default the unpreserved bits are overwritten by the value of preserved bits. For instance, if you preserve the P bits, the IP precedence bits are overwritten with the value of the P bits. To preserve the IP precedence bits, use the no mls qos rewrite ip dscp command. The no mls qos rewrite ip dscp command is not compatible with the MPLS and MPLS VPN features.

•EoMPLS is not supported with private VLANs.

•The following restrictions apply to using trunks with EoMPLS:

–To support Ethernet spanning tree bridge protocol data units (BPDUs) across an EoMPLS cloud, you must disable spanning tree for the Ethernet-over-MPLS VLAN. This ensures that the EoMPLS VLANs are carried only on the trunk to the customer switch. Otherwise, the BPDUs are not directed to the EoMPLS cloud.

•Unique VLANs are required across interfaces. You cannot use the same VLAN ID on different interfaces.

•EoMPLS tunnel destination route in the routing table and the CEF table must be a /32 address (host address where the mask is 255.255.255.255) to ensure that there is a label-switched path (LSP) from PE to PE.

•For a particular EoMPLS connection, both the ingress EoMPLS interface on the ingress PE and the egress EoMPLS interface on the egress PE have to be subinterfaces with dot1Q encapsulation or neither is a subinterface.

•802.1Q in 802.1Q over EoMPLS is supported if the outgoing interface connecting to MPLS network is a port on an Layer 2 card.

•Shaping EoMPLS traffic is not supported if the egress interface connecting to an MPLS network is a Layer 2 LAN port (a mode known as PFC-based EoMPLS).

•EoMPLS based on a PFC does not perform any Layer 2 lookup to determine if the destination MAC address resides on the local or remote segment and does not perform any Layer 2 address learning (as traditional LAN bridging does).

Information About EoMPLS

AToM Overview

Any Transport over MPLS (AToM) transports Layer 2 packets over an MPLS backbone. AToM uses a directed Label Distribution Protocol (LDP) session between edge routers for setting up and maintaining connections. Forwarding occurs through the use of two level labels that provide switching between the edge routers. The external label (tunnel label) routes the packet over the MPLS backbone to the egress PE at the ingress PE. The VC label is a demuxing label that determines the connection at the tunnel endpoint (the particular egress interface on the egress PE as well as the VLAN identifier for an Ethernet frame).

EoMPLS Overview

EoMPLS is one of the AToM transport types. EoMPLS works by encapsulating Ethernet PDUs in MPLS packets and forwarding them across the MPLS network. Each PDU is transported as a single packet. Cisco IOS Release 15.1SY supports two EoMPLS modes:

•VLAN mode—Transports Ethernet traffic from a source 802.1Q VLAN to a destination 802.1Q VLAN through a single VC over an MPLS network. VLAN mode uses VC type 5 as default (no dot1q tag) and VC type 4 (transport dot1 tag) if the remote PE does not support VC type 5 for subinterface (VLAN) based EoMPLS.

•Port mode—Allows all traffic on a port to share a single VC across an MPLS network. Port mode uses VC type 5.

Note For both VLAN mode and port mode, EoMPLS in Cisco IOS Release 15.1SY does not allow local switching of packets between interfaces unless you use loopback interfaces.

•To verify that the PE router endpoints have discovered each other, enter the show mpls ldp discovery command. When an PE router receives an LDP hello message from another PE router, it considers that router and the specified label space to be "discovered."

Router# show mpls ldp discovery

Local LDP Identifier:

13.13.13.13:0

Discovery Sources:

Interfaces:

GE-WAN3/3 (ldp): xmit/recv

LDP Id: 12.12.12.12:0

Targeted Hellos:

13.13.13.13 -> 11.11.11.11 (ldp): active/passive, xmit/recv

LDP Id: 11.11.11.11:0

•To verify that the label distribution session has been established, enter the show mpls ldp neighbor command. The third line of the output shows that the state of the LDP session is operational and shows that messages are being sent and received.

Router# show mpls ldp neighbor

Peer LDP Ident: 12.12.12.12:0; Local LDP Ident 13.13.13.13:0

TCP connection: 12.12.12.12.646 - 13.13.13.13.11010

State: Oper; Msgs sent/rcvd: 1649/1640; Downstream

Up time: 23:42:45

LDP discovery sources:

GE-WAN3/3, Src IP addr: 34.0.0.2

Addresses bound to peer LDP Ident:

23.2.1.14 37.0.0.2 12.12.12.12 34.0.0.2

99.0.0.1

Peer LDP Ident: 11.11.11.11:0; Local LDP Ident 13.13.13.13:0

TCP connection: 11.11.11.11.646 - 13.13.13.13.11013

State: Oper; Msgs sent/rcvd: 1650/1653; Downstream

Up time: 23:42:29

LDP discovery sources:

Targeted Hello 13.13.13.13 -> 11.11.11.11, active, passive

Addresses bound to peer LDP Ident:

11.11.11.11 37.0.0.1 23.2.1.13

•To verify that the label forwarding table is built correctly, enter the show mpls forwarding-table command to verify that a label has been learned for the remote PE and that the label is going from the correct interface to the correct next-hop.

Router# show mpls forwarding-table

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 Untagged 223.255.254.254/32 \

0 Gi2/1 23.2.0.1

20 Untagged l2ckt(2) 133093 Vl2 point2point

21 Untagged l2ckt(3) 185497 Vl3 point2point

24 Pop tag 37.0.0.0/8 0 GE3/3 34.0.0.2

25 17 11.11.11.11/32 0 GE3/3 34.0.0.2

26 Pop tag 12.12.12.12/32 0 GE3/3 34.0.0.2

The output shows the following data:

–Local tag—Label assigned by this router.

–Outgoing tag or VC—Label assigned by next hop.

–Prefix or Tunnel Id—Address or tunnel to which packets with this label are going.

–Bytes tag switched— Number of bytes switched out with this incoming label.

–Outgoing interface—Interface through which packets with this label are sent.

–Next Hop—IP address of neighbor that assigned the outgoing label.

•To display the state of the currently routed VCs, enter the show mpls l2transport vc command.

•To verify that the PE router endpoints have discovered each other, enter the show mpls ldp discovery command. When an PE router receives an LDP Hello message from another PE router, it considers that router and the specified label space to be "discovered."

Router# show mpls ldp discovery

Local LDP Identifier:

13.13.13.13:0

Discovery Sources:

Interfaces:

GE-WAN3/3 (ldp): xmit/recv

LDP Id: 12.12.12.12:0

Targeted Hellos:

13.13.13.13 -> 11.11.11.11 (ldp): active/passive, xmit/recv

LDP Id: 11.11.11.11:0

•To verify that the label distribution session has been established, enter the show mpls ldp neighbor command. The third line of the output shows that the state of the LDP session is operational and shows that messages are being sent and received.

Router# show mpls ldp neighbor

Peer LDP Ident: 12.12.12.12:0; Local LDP Ident 13.13.13.13:0

TCP connection: 12.12.12.12.646 - 13.13.13.13.11010

State: Oper; Msgs sent/rcvd: 1715/1706; Downstream

Up time: 1d00h

LDP discovery sources:

GE-WAN3/3, Src IP addr: 34.0.0.2

Addresses bound to peer LDP Ident:

23.2.1.14 37.0.0.2 12.12.12.12 34.0.0.2

99.0.0.1

Peer LDP Ident: 11.11.11.11:0; Local LDP Ident 13.13.13.13:0

TCP connection: 11.11.11.11.646 - 13.13.13.13.11013

State: Oper; Msgs sent/rcvd: 1724/1730; Downstream

Up time: 1d00h

LDP discovery sources:

Targeted Hello 13.13.13.13 -> 11.11.11.11, active, passive

Addresses bound to peer LDP Ident:

11.11.11.11 37.0.0.1 23.2.1.13

•To verify that the label forwarding table is built correctly, enter the show mpls forwarding-table command.

Router# show mpls forwarding-table

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 Untagged 223.255.254.254/32 \

0 Gi2/1 23.2.0.1

20 Untagged l2ckt(2) 55146580 Vl2 point2point

24 Pop tag 37.0.0.0/8 0 GE3/3 34.0.0.2

25 17 11.11.11.11/32 0 GE3/3 34.0.0.2

26 Pop tag 12.12.12.12/32 0 GE3/3 34.0.0.2

•The output displays the following data:

–Local tag—Label assigned by this router.

–Outgoing tag or VC—Label assigned by next hop.

–Prefix or Tunnel Id—Address or tunnel to which packets with this label are going.

–Bytes tag switched— Number of bytes switched out with this incoming label.

–Outgoing interface—Interface through which packets with this label are sent.

–Next Hop—IP address of neighbor that assigned the outgoing label.

•To display the state of the currently routed VCs, enter the show mpls l2transport vc command: